Hermetic sealing is always a key issue determining service life of a Lithium-ion battery since a high voltage of the battery renders water decomposition or oxygen reduction if water or oxygen molecules are present in the electrolyte. Such problems are often caused by improper cell sealing. Conventionally, lithium cells are small in size and capacity. Taking type 18650 cylindrical cells as an example, the cell size is 18 mm in diameter and 65 mm in height. The cell capacity ranges from about 2.8 Ah to 1.4 Ah, according to the types of cathode materials being used for the cells. In view of the limitation of space utilized for cover construction, the metal to polymer interface at current collecting posts of the battery is usually small (only through the support of an insulation layer shaped like an O-ring) and therefore the interface can not provide a lengthy diffusion path for oxygen, water molecules or other gases or liquids penetrating through the metal to polymer interface. The situation becomes worse once a continuous high temperature cycling condition is applied to the cells (e.g. conditions such as continuous high power operation) owing to the accelerated degradation of the polymer to metal interface. The same problem is applicable for other types of lithium ion cells such as prismatic cells or even lithium polymer cells.